The proposed investigation is a continuation of work undertaken to gain an understanding of the genetic characteristics and mechanisms of certain Cyanophytes. Using unicellular species of the genera Anacystis and Synechococcus various auxotrophic, conditional and other mutant strains have been and are being isolated and characterized biochemically. With these mutants, genetic mapping is being carried out and linkage relationships determined by means of genetic transformation. The resulting map may hopefully aid in a determination of the nature of the genetic apparatus in these organisms. A recently discovered conjugation-like process will be analyzed for its possible use as a further tool in genetic analysis, and the search for a temperate virus capable of transduction will be continued as well.